The present invention relates generally to the field of lithography, and more particularly, to laser controlled nanolithography.
One key for the rapid development of modern computer technology has been the constant miniaturization of electronic devices and integrated circuits. Heretofore, photolithography has been the conventional method for industrial integrated circuit production. However, it is becoming clear that photolithography has significant, if not unsurmountable challenges when feature sizes below 50 nm are required. Alternative lithographic techniques are needed.
In atomic lithography, conventional roles played by light and matter are reversed. Instead of using a solid mask to pattern a light beam, a mask of light is used to pattern a beam of neutral atoms. Previously, researchers have shown that atomic lithography can be used to pattern long thin features or strips, as shown in FIG. 1. In addition, researchers have been able to pattern an array of features, as shown in FIG. 2. Features such as those illustrated in FIGS. 1 and 2 can be formed by exposing a source of atoms, such as chromium or aluminum, from an oven to a substrate using atomic lithography.
FIG. 3 illustrates a schematic representation of a prior atomic lithography process. See, Th. Schulze, et al., xe2x80x9cWriting a Superlattice with Light Forces,xe2x80x9d Applied Physics B, Lasers and Optics, Vol. 70, 2000, pp. 671-674. Opposing laser beams 20 and 21, which can be produced by reflecting a single laser beam back on itself, produce a transversal laser cooling of atoms near an oven 24. In addition, laser beams 25 and 26 produce a standing wave 30 above a substrate 31. Atoms from the oven 24, shown by arrows, are directed through the standing wave 30 prior to reaching the substrate 31. The transversal laser cooling collimates (i.e., lines up) the atomic beam. As a result of the focusing effect of the standing wave 30, the atoms are deposited on the surface of the substrate 31 in parallel lines 32. The linear pattern of the deposited atoms corresponds to the minima or maxima of the standing wave 30 due to the fact that the atoms are optically focused toward the minima or maxima of the standing wave.
In optical lithography, arbitrary and aperiodic patterning of atoms is produced by projecting the desired optical intensity distribution using a lens in front of the target substrate. Although atomic lithography processes have many attractive features, one major limitation is that heretofore only spatially periodic patterning has been demonstrated.
To be able to utilize atomic lithography to replace optical lithography, it thus would be necessary to be able to deposit atomic species in arbitrary patterns. It would be particularly advantageous to be able to control the position of atom spot deposition without mechanical motion. Such control would allow the application of atomic lithography to a greater range of fabrication tasks.
The present invention can be embodied in a method of depositing atoms on a substrate. The method includes forming an atomic beam, providing a laser beam above a surface of the substrate where the laser beam has a direction defined by at least one spatial light modulator through which the laser beam passes to form a high intensity optical spot by interference to selectively focus the collimated atomic beam, and synthesizing a spot that can be moved to form a two-dimensional pattern of atoms on the surface of the substrate.
The present invention can also be embodied in an atomic lithography system that can be configured to form arbitrary two-dimensional nanostructures on a substrate. The system includes spatial light modulators and lenses positioned proximate the spatial light modulators. The lenses and spatial light modulators are configured to selectively focus atoms in an atomic beam onto the substrate.
The present invention can also be embodied in an deposition system comprising means for forming an atomic beam, means for directing a laser beam above a surface of a substrate to selectively focus the atomic beam, and means for synthesizing a spot for forming a pattern of atoms on the surface of the substrate.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.